- From: Dan Connolly <connolly@w3.org>
- Date: Thu, 02 Jun 2005 08:37:42 -0500
- To: Yoshio FUKUSHIGE <fuku@w3.org>
- Cc: public-rdf-dawg@w3.org
On Thu, 2005-06-02 at 19:12 +0900, Yoshio FUKUSHIGE wrote: [...] > aggregator. > 8.4 > [[ > Each time a graph is read into the aggregator, it is given a URI by the > local system. > ]] > but, so it may not be the same URI the graph had BEFORE being aggregated, > which means we cannot know the name of a named graph without asking (but > how?) ! This reminds me of something I have been meaning to comment on... perhaps not exactly the same issue, but nearby... If I write SELECT ?who FROM NAMED <alice> <bob> WHERE GRAPH <alice> { <alice#me> foaf:knows ?who } GRAPH <bob> { <bob#me> foaf:knows ?who } then we've got two (or more) "named graphs" in the dataset. This suggests that (the absolute form of) <alice> is a/the name of a graph. This is somewhat misleading, w.r.t. web architecture, which says that <alice> identifies a resource that has a representation that is a graph. The query might be run twice and get two different answers because the state of the <alice> resource changed; i.e. it was represented by a different graph. So to say that <alice> is the name of a graph is a little goofy. cwm uses a log:semantics property to make the indirection explicit. I don't suggest we go there in SPARQL, but in http://lists.w3.org/Archives/Public/semantic-web/2005Jun/0004 I see > E.g. using TriG, the dataset from Example 1 in section 7.1 of > the SPARQL spec could be unambiguously serialized as: ... > :bg > { > <http://example.org/bob> dc:publisher "Bob" . > <http://example.org/alice> dc:publisher "Alice" . > } and the TriG spec (http://www.wiwiss.fu-berlin.de/suhl/bizer/TriG/ ) says that's short for :bg :- { ... } which pretty much means :bg owl:sameAs { ... } but the in a SPARQL dataset, the relationship is more like :bq log:semantics { ... } I haven't thought of any actual replacement for the "named" terminology, so I'll suggest a note ala: NOTE: The "FROM NAMED" syntax suggests that the URI identifies the corresponding graph, but actually the relationship between a URI and a graph in an RDF dataset is indirect: the URI identifies a resource, and the resource is represented by a graph (or, more precisely: by a document that serializes a graph). See also the diagram in section "1. Introduction" of [webarch]. Hmm... bummer that diagram doesn't have a number/label. http://www.w3.org/TR/webarch/#intro -- Dan Connolly, W3C http://www.w3.org/People/Connolly/ D3C2 887B 0F92 6005 C541 0875 0F91 96DE 6E52 C29E
Received on Thursday, 2 June 2005 13:37:51 UTC